Friday, September 17, 2010

Regular pterophiles will realise that this is just a direct re-post from my own blog. However, the more dedicated pterosaur blog hound might not have seen this, so here's the post in all it's glory.

Proof, if it were needed, that the Pterosaur.net team do actually work on pterosaurs and not just blab endlessly about them comes from todays new paper featureing Ross Elgin, myself and Dino Frey. Once more, this is an odd time to talk about it since what has actually turned up are the uncorrected proofs, but it is out there and being read, so now is the time to talk about it. (You can download and read it here, and a very old post of mine here might be a good primer if you don't know your pterosaur wings too well).

Friday, September 10, 2010

I've tried to be good. No blogging for a bit while I catch up with work/job applications/dismantling the oven to clean it properly, but Ashley Fragomeni, aka Paleochick, has just gone and blown the whole thing. Her antics over at The Paleochick's Digs mean that, instead of finishing the Euparkeria skeletal reconstruction I need for my book, I'm now telling you about her ROFLopterosauria series, an collision of my pterosaur palaeoart and erudite observations into pterosaur palaeobiology. The latest one was just too funny to ignore, so here we are. On the internet. Blogging. Now my book won't be finished on time, I won't get paid, I won't make the rent and I'll be forced to sell my kidneys (both of them) and other parts of my body to make ends meet. Thanks a lot, Dusty.

We're promised a new bit of ROFLopterosauria every day or so for the next few days, so be sure to head back to the Paleochick's Digs over the next week to see more. The image above has nothing to do with anything you've just read, but shows Peter Wellnhofer's Rhamphorhynchus mobile on display in the Palaeontology Museum, Munich. We can't, after all, have a dull-looking blog post, can we?

Saturday, September 4, 2010

I was very happy to find that my airline had provided me with my own little TV screen and a selection of movies for my flight back from Flugsaurier 2010. With eight hours to kill, this was welcome news and, as soon as we were away and provided with those annoying little earbud headphones that never really fit your ears properly, I was off to Movieland. First up: the remake of Clash of the Titans, a flick that I’d not heard great things about but promised nice visuals, minimal cerebral action and plenty of nice CG creatures. The reviews I’d read were spot on: clichéd characters, dialogue so wooden it could serve as a useful boat oar and numerous clumsy attempts to cash in on the 3D bandwagon kicked off by Avatar. Still, it did feature a nicely rendered Pegasus, giant scorpion caravans and Medusa, a snake-woman hybrid that I found worryingly attractive. Most concerning is that it wasn’t just the top half that made for the most pleasant viewing (which would be understandable, given that her appearance was based on model Natalia Vodianova): there’s clearly a part of my psyche, unrecognised until a week or so ago, that really digs the thought of scantily-clad snakewomen sliding and coiling around their room and constricting visitors to their chambers. Imagine how touchy-feely that would be: you’d not mind having a late breakfast with that. Man, that' d be a night to remember. Just think of the... oh… wait a second. Oh yeah: pterosaurs. Blog post. Decency. No mythophilic filth. Got it.

Next up: last year's Star Trek reboot. Now, I’ve never seen eye-to-eye with Star Trek. I was once a massive fan of Star Wars, but Trek? No. Just couldn’t get into it. Lots of talking; uniforms that looked a bit like the pyjamas I used to wear; big, lumbering spaceships that fire weedy looking weapons; aliens that look just like people with pies glued to their foreheads and, most importantly, a distinct lack of Han Solo. Bottom line: I just found it a bit dull so, when I heard the whole thing was being rebooted I wasn’t terribly excited by the idea. Still, the reviews were pretty good so I thought I’d give it a whirl. I did, after all, have several hours of flight time to kill.

You know what? It was great. It was exciting. It had proper aliens and gripping, tense action scenes. It had Simon Pegg. It wasn’t clean cut: there was even a bit of proper, honest-to-goodness swearing. I was totally surprised and, while I’m unlikely to change my opinion on the other entries in the franchise, I’ll certainly give the 2012 Trek sequel a spin. I may even pay to see it at the cinema. You know: with my own money and everything.

And the new Star Trek is just like pterosaur specimen n. 12701a of the Ligabue collection

Seriously. For the uninitiated, n. 12701a is a tiny distal fragment of a pterosaur wing phalanx one from the Santana Formation of Brazil (described by Dalla Vecchia and Ligabue 1993; n. 12701a shown in adjacent line drawing). When I say fragment, I’m not kidding: it’s really is one of the most unremarkable, dull and uninteresting scraps of pterosaur fossil ever published on and, like the old Star Trek, it’s the sort of thing that we should only really be bothered about when there’s no reruns of The Simpsons on the telly. In fact, probably the only thing stopping n. 12701a from being totally forgotten about is its size: for a distal fragment of a wing phalanx, it’s huge. At 75 mm across, Dalla Vecchia and Ligabue reconstructed the length of the complete phalanx as 850 mm (based on ornithiocheiroids such as Pteranodon and Santanadactylus), a dimension almost twice the size of comparable elements from 4 -5 m span ornithocheirids. Using complete ornithocheirid wings as a guide, the authors then went on to suggest that tiny-little-fragment n. 12701a represents an animal with a whopping 8 – 9 m wingspan.

Now, in a world where the largest pterosaurs span something like 10 m, the predicted wingspan of n. 12701 isn’t really a big deal. What is, however, is its age: aside from this and some other problematic remains from Britain*, there are no accounts of giant pterosaurs in the Lower Cretaceous. Hence, n. 12701 suggests that sizes pretty-near comparable with the largest pterosaurs of all were achieved tens of millions of years before Pteranodon and the giant azhdarchids turn up. All of a sudden, then, that chunk of pterosaur is starting to look far less pre-2009 Star Trek-esque and far more akin to the 2009 reboot: it's exciting, interesting and, being the lone wolf for giant pterosaurs of this time, a touch edgy. Indeed, people have probably been getting excited about n. 12701a for some time: I wouldn’t be surprised if it influenced the decision to portray Ornithocheirus with a 10 m span in Walking with Dinosaurs, for instance (see image at the top of the post, from here).

*There is one additional claim for giant pterosaurs in the Lower Cretaceous based on very, very scrappy material from the Isle of Wight, UK (Martill et al. 1996). We don’t have time to go into the details here, but there’s good reason to think that these remains were not from giant animals. The rationale for this has been written up by myself, Dave Martill and Steve Sweetman and should be published next year.

Alas, n. 12701a may not be quite as New Trek as we all thought. To be honest, I’ve never been fully convinced that it demonstrated giant pterosaurs were present in the Lower Cretaceous: it’s just so scrappy that drawing any conclusions about its overall size seems extremely spurious. A little bit of further investigation reveals why this gut feeling may be right.

That was then: this is nowTo begin with, there no way that n. 12701a can be allocated to any pterosaur group: it’s just too scrappy and undiagnostic (Dalla Vecchia and Ligabue stated this themselves, but it bears reiterating here because it will prove important later). It is probably sensible to suspect it represents a group known from the Santana Formation, meaning it could either represent an ornithocheirid or an azhdarchoid. Now, in 1993, the Santana Formation was mainly known for its ornithocheirids (e.g. Unwin 1988) and azhdarchoids were relatively new kids on the block (Kellner and Campos 1988; Kellner 1989). Since then, however, we’ve found much more azhdarchoid material including up to three new species (Kellner and Campos 1994, 2002; Witton 2009), complete skeletons (Kellner and Hasagawa 1993) and buckets of incomplete specimens that are sitting in museum stores. This suggests that azhdarchoids were a far more speciose and abundant component of the Santana Formation pterosaur assemblage than could be predicted in the early ‘90s, then, and this is means that we need to strongly consider that n. 12701a may have azhdarchoid affinities.

This is potentially quite a big deal because azhdarchoids and ornithocheirids have very different wing constructions (see diagram of pterodactyloid wing configurations, above. The top image shows the ornithocheirid wingplan; middle image, the azhdarchid wingplan; bottom, tapejarid wingplan. From Witton [2007]). The wing phalanges of ornithocheirids are far more proportionate along the length of the wing finger, decreasing in size distally but only by comparatively small measures (e.g. Wellnhofer 1985). Azhdarchoids, by contrast, have massive first phalanges in their wing fingers (occupying over 40 per cent of the total finger length) but then drastically reduced second, third and fourth elements (Unwin 2003; Kellner 2003). What’s more, the diameters of the distal wing phalanges decrease in size dramatically across the azhdarchoid wing: that of the first is proportionally enormous compared to the rest. What this is leading up to, then, is that an azhdarchoid could have a massive first wing phalanx like that represented by n. 12701a without being a pterosaur giant. In fact, scaling an azhdarchoid wing using the 850 mm-long first phalanx length predicted by Dalla Vecchia and Ligabue gives a single wing length of just 3 m, and, therefore, a total wingspan of 6 m. That’s big, sure, but hardly gigantic for a pterosaur. Plus, this estimate supposes that the 850 mm length reconstuction of n 12701a is appropriate: would the same estimate be generated if it were based on a non-ornithocheirid pterosaur?

The plot thickens further when we consider that large azhdarchoids are already known from the same locality as n. 12701a. The Santana Formation thalassodromid Thalassodromeus, in particular, is a huge animal with a jaw approaching a metre in length (see image, above, of the author posing in a most embarrassing fashion with a full-size Thalassodromeus bust). Estimating the wingspan for this animal is difficult as no postcranial material is known, but its skull proportions suggest a 5 m span (Kellner and Campos 2002). Given how little data we have regarding the proportions between neoazhdarchian skulls and wingspans, it may not be entirely crazy to suppose a 6 m wingspan, either. Along with everything else, then, there are pterosaurs in the Santana Formation that would be a good size match for n. 12701a if it were, indeed, an azhdarchoid.

So, Lower Cretaceous giant pterosaurs, then?None of this delivers a death-blow to the idea of giant pterosaurs existing in the Lower Cretaceous of course, but it certainly suggests that there is an equally, if not more, parsimonious interpretation of n. 12701a than it being the sole remnant of a giant ornithocheirid species. If nothing else, ornithocheirids are among the best represented of all pterosaurs and, in our extensive sampling of them, there’s no other evidence for such enormous animals (at least, none that I’m aware of). Considering n. 12701a as an azhdarchoid is a far more believable interpretation: it scales to a wingspan that we know azhdarchoids achieved, we would expect its overly large proportions in an azhdarchoid wing and, indeed, there are even comparably sized azhdarchoids in the same deposit. As such, while I’m not going to rule out the evolution of giant pterosaurs in the Lower Cretaceous entirely, I think we need far more evidence that we currently have to consider their existence likely.

And that, folks, is it for now. It’s Saturday night, so I’ll take my tale of how n. 12701a went from being boring to being really exciting and then boring again to the pub. Hey, you never know: there may be some women down there that, from the waist down, resemble rattlesnakes. You never know. I need to get ready. Clean, ironed shirt? Check. Wallet, house keys and phone? Check. Reflective shield and anti-venom? Check. Right, toodles.

Witton, M. P. 2009. A new species of Tupuxuara (Thalassodromidae, Azhdarchoidea) from the Lower Cretaceous Santana Formation of Brazil, with a note on the nomenclature of Thalassodromidae. Cretaceous Research, 30, 1293-1300.